Other populations show dips in asthma rates

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Childhood asthma prevalence has stopped increasing in recent years, and the non-Hispanic black-white disparity stopped increasing due mainly to plateauing prevalence among non-Hispanic black children.

While overall asthma prevalence has declined, recent trends indicate increases among poor children, older children, and those living in the South.

While overall asthma prevalence has declined, recent trends indicate increases in the condition among poor children and older children, a retrospective analysis of National Health Interview Survey data from 2001-2013 found.

Using adjusted multivariate models, Lara J. Akinbami, MD, of the CDC, and colleagues found a significantly increasing linear trend in asthma prevalence, particularly in the middle of the time period, for poor children (defined as family income <100% of the federal poverty level) and children ages 10-17.

Examining recent data (2009-2013), there were significant interactions with time among race/ethnicity and geographic region, in addition to age group and poverty status, the authors reported in Pediatrics.

Overall, asthma prevalence among 0-17 year olds increased from 2001 to 2009, but plateaued after 2008 and declined significantly by 2013, when it was 8.3% (SE 0.3%). This is a reversal of earlier trends from 1980-1995, when childhood asthma prevalence across the entire national population more than doubled.

The authors offer a number of hypotheses for these recent trends, including improved identification of asthma, as well as the hygiene hypothesis and increased sensitization to indoor allergens.

"There is general consensus that no single explanation is likely to suffice and that the story of changing asthma prevalence is one of interplay between complex factors," they wrote. "This analysis of NHIS data cannot answer the question of why trends change, but does provide a comprehensive national picture and some insight into the complexity of asthma prevalence."

There were also significant quadratic trends (i.e., nonlinear trends best modeled with quadratic equations) in asthma prevalence for near-poor children (family income 100%-200% of FPL), with prevalence increasing at the beginning of the time period but not changing significantly thereafter. Nonpoor children (≥200% of FPL) exhibited similar trends, although prevalence declined at the end of the time period.

Quadratic trends were significant for younger children ages 0-4 and 5-9 years. However, asthma prevalence for the youngest children decreased significantly at the end of the time period following an increase, while it recently plateaued among 5-9 year olds.

The authors state that adverse asthma outcomes, such as emergency department visits and hospitalizations, have been higher among younger children.

"A changing trend in asthma prevalence among 0- to 4-year olds and 5- to 9-year olds may also have a positive impact on the number of children in these age groups who experience asthma-related health care visits and associated costs," they wrote.

Racial disparities were also observed in asthma prevalence after 2001, though the authors note that these differences seemed to have stopped increasing after 2009. But significant quadratic trends were associated with non-Hispanic black and Mexican-American children. There were no significant trends in asthma prevalence for non-Hispanic white or Puerto Rican children.

Demographically, asthma prevalence was highest among Puerto Rican children, followed by non-Hispanic black children. In 2011, the prevalence ratio between non-Hispanic black and white children was 2.1% (95% CI 1.7-2.4), which was the greatest disparity throughout the time period. The authors cite the "notable pattern" of this increasing prevalence in non-Hispanic black children, rising from a 40% higher relative disparity in 2001 to a 100% higher disparity in 2010, relative to non-Hispanic white children.

Geographically, children living in the South were associated with an increasing linear trend in asthma prevalence, while children in the Midwest exhibited a quadratic trend. No significant trends were observed for children in the Northeast and West.

Data from 152,387 children was included in the study, with asthma prevalence measured through affirmative responses to two questions: "Has a doctor or other health professional ever told you that your child has asthma?" and "Does your child still have asthma?"

Besides this reliance on unconfirmed, proxy-reported information, other limitations to the study included the small number of years available to assess a change in trend late in the analyzed time period and, during the study period, a change in the survey question to assess asthma prevalence.

The authors indicate they have no potential conflicts of interest to disclose.

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